The engine employed on a construction vehicle, such as a tractor, has a filter assembly mounted thereon to continuously filter oil during operation of the engine. As shown in FIG. 4 of applicant's drawing, the filter assembly may comprise a base B attached on the engine and a case C, enclosing a cartridge-type filter, mounted on the base. The open end of the case is disposed within an annular recess R formed on the base and a seal S is disposed within the recess and is compressed therein by the case.
Since the wall thickness of the case is less than the width of the recess, the case is oftentimes mounted on the base in an off-center relationship indicated at C' whereby a portion S' of the seal is extruded on one side of the case. Such extrusion gives rise to obvious sealing problems and the seal is usually sufficiently deformed and damaged so that it cannot be reused. In addition, upon replacement of the filter, a tool must be used to scrape the remnants of seal S out of recess R which not only increases service time but also damages the sealing surfaces defined by the recess.